Electrowetting display device

ABSTRACT

An electrowetting display device includes a black matrix that includes a plurality of openings corresponding to pixels, respectively, a first extension portion extending in a driving direction of an electrowetting layer, the driving direction being a direction in which motion of the electrowetting layer is induced when a voltage difference is applied between a common electrode and a pixel electrode, and a partition wall that partitions the pixels. The first extension portion includes first and second areas respectively extending in opposite directions to each other and a third area having a width substantially the same as a width of the partition wall. The first area has a width less than about half of a first length corresponding to a length extending between both sides of each pixel in the driving direction, and the second area has a width less than the width of the first area.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 to Korean Patent Application No. 10-2012-0066245, filed onJun. 20, 2012, the contents of which are hereby incorporated byreference.

BACKGROUND

1. Field of Disclosure

Embodiments of the present disclosure relate generally to flat paneldisplay devices. More particularly, embodiments of the presentdisclosure relate to an electrowetting display device having improveddriving speed.

2. Description of the Related Art

Contemporary flat panel displays can employ various technologies.Examples of these various display devices are a liquid crystal displaydevice, an organic light emitting display device, an electrowettingdisplay device, a plasma display panel, an electrophoretic displaydevice, etc.

Among them, the electrowetting display device has been spotlighted as anext generation display device since it has certain desirableproperties, e.g., fast response speed, low driving voltage, lowthickness, etc., when compared to the liquid crystal display device. Theelectrowetting display device utilizes a basic principle that water andoil do not mix.

The electrowetting display device typically includes first and secondsubstrates facing each other, and an electrowetting layer disposedbetween the first and second substrates. The first substrate includespixel electrodes respectively corresponding to pixels. The secondsubstrate includes a common electrode and a black matrix. According tovoltages applied to the pixel electrodes and the common electrode, amovement of the electrowetting layer is controlled, so desired imagesare displayed on the electrowetting display.

SUMMARY

The present disclosure provides an electrowetting display device havingimproved driving speed.

Embodiments of the inventive concept provide an electrowetting displaydevice that includes a first base substrate that includes a plurality ofpixels, a second base substrate that faces the first base substrate andincludes a common electrode, an electrowetting layer disposed betweenthe first base substrate and the second base substrate, a plurality ofpixel electrodes disposed on the first base substrate to respectivelycorrespond to the pixels, and a black matrix. The black matrix includesa plurality of openings corresponding to respective ones of the pixels,the black matrix having a first extension portion extending in a drivingdirection of the electrowetting layer, the driving direction being adirection in which motion of the electrowetting layer is induced when avoltage difference is applied between the common electrode and thecorresponding pixel electrode, and extending in a second directionsubstantially perpendicular to the driving direction. The firstextension portion includes a first area, a second area, and a thirdarea. The first area and the second area respectively extend in oppositedirections to each other, the third area has a width substantially thesame as a width of the partition wall, the first area has a width lessthan about half of a first length corresponding to a length extendingbetween both sides of each pixel in the driving direction of theelectrowetting layer, and the second area has a width less than thewidth of the first area.

The black matrix can further comprise a second extension portionextending between adjacent ones of the first extension portions, thefirst extension portion can have a width greater than a width of thesecond extension portion, and the third area can overlaps the partitionwall.

The partition wall can be disposed on the black matrix, can include asame material as the black matrix, and can have a black color.

The electrowetting display device can further include an insulatinglayer disposed on the first base substrate to cover the pixel electrodesand a hydrophobic layer disposed in the openings, and the black matrixand the hydrophobic layer can both be disposed on the insulating layer.

The electrowetting layer can include a first fluid that has electricalnon-conductivity or non-polarity and a second fluid immiscible with thefirst fluid and having electrical conductivity or polarity. The firstfluid can be accommodated in a space defined by the partition wall, andthe second fluid can be disposed on the first fluid.

When a common voltage is applied to the common electrode and one or moregray-scale voltages are applied to the pixel electrodes, the secondfluid can contacts the hydrophobic layer and the first areas so as topush the first fluid to a side portion of the pixels.

The second area can extends under an area in which the first fluid isgathered, so as to overlap the first fluid.

Embodiments of the inventive concept provide an electrowetting displaydevice that includes a first base substrate that includes a plurality ofpixels, a second base substrate that faces the first base substrate andincludes a common electrode, an electrowetting layer disposed betweenthe first base substrate and the second base substrate, a plurality ofpixel electrodes disposed on the first base substrate to respectivelycorrespond to the pixels, and a black matrix. The black matrix isdisposed between the common electrode and the second base substrate andincluding a plurality of openings corresponding to respective ones ofthe pixels, the black matrix having a first extension portion extendingin a driving direction of the electrowetting layer, the drivingdirection being a direction in which motion of the electrowetting layeris induced when a voltage difference is applied between the commonelectrode and the corresponding pixel electrode, and extending in asecond direction substantially perpendicular to the driving direction.The first extension portion includes a first area, a second area, and athird area. The first area and the second area respectively extend inopposite directions to each other, the third area has a widthsubstantially the same as a width of the partition wall, the first areahas a width less than about half of a first length corresponding to alength extending between both sides of each pixel in the drivingdirection of the electrowetting layer, and the second area has a widthless than the width of the first area.

According to the above, the electrowetting display device may haveimproved driving speed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view showing an electrowetting display deviceaccording to a first exemplary embodiment of the present invention;

FIG. 2 is an enlarged perspective view showing a portion of theelectrowetting display device shown in FIG. 1;

FIG. 3A is a plan view showing a reset state of a pixel of theelectrowetting display device shown in FIG. 1;

FIG. 3B is a cross-sectional view taken along a line I-I′ shown in FIG.3A;

FIG. 4A is a plan view showing a driving state of a pixel of theelectrowetting display device shown in FIG. 1;

FIG. 4B is a cross-sectional view taken along a line II-II′ shown inFIG. 4A;

FIG. 5A is a plan view showing a movement of an electrowetting layer ofa pixel in a reset state;

FIG. 5B is a cross-sectional view taken along a line III-III′ shown inFIG. 5A;

FIG. 6 is a cross-sectional view showing an electrowetting displaydevice according to a second exemplary embodiment of the presentinvention;

FIG. 7 is a cross-sectional view showing an electrowetting displaydevice according to a third exemplary embodiment of the presentinvention; and

FIG. 8 is a cross-sectional view showing an electrowetting displaydevice according to a fourth exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 is a perspective view showing an electrowetting display deviceaccording to a first exemplary embodiment of the present invention.

Referring to FIG. 1, an electrowetting display device 100 includes afirst substrate 110 in which a plurality of pixels PXs is defined in amatrix form, a second substrate 120 facing the first substrate 110, andan electrowetting layer 130 interposed between the first substrate 110and the second substrate 120. Hereinafter, one pixel is indicated by PXand two or more pixels are indicated by PXs.

The pixels PXs are arranged in n rows by m columns. Here, n and m areinteger numbers greater than zero (0). The pixels PXs are configured toinclude red, green, and blue pixels. The red, green, and blue pixels areregularly and repeatedly arranged in a row direction and a columndirection, but the arrangement of the pixels PXs should not be limitedthereto or thereby. Embodiments of the invention contemplate anycombinations and arrangements of any colored pixels.

FIG. 2 is an enlarged perspective view showing a portion of theelectrowetting display device shown in FIG. 1.

Referring to FIG. 2, the first base substrate 110 includes a first basesubstrate 111, a plurality of pixel electrodes PEs, an insulating layer112, a black matrix BM, a hydrophobic layer 113, and a partition wallWA. Hereinafter, one pixel electrode is indicated by PE and two or morepixel electrodes are indicated by PEs.

The first base substrate 111 may be a transparent insulator and formedof a polymer, e.g., glass or plastic. In the case that the first basesubstrate 111 is a plastic substrate, the first base substrate 111 canbe configured to include polyethylene terephthalate (PET), fiberreinforced plastic (FRP), or polyethylene naphthalate (PEN).

The pixel electrodes PEs are disposed on the first base substrate 111.The pixel electrodes PEs respectively correspond to the pixels PXs andare applied with gray-scale voltages.

The pixel electrodes PEs include a transparent conductive material, suchas indium tin oxide (ITO), conductive polymer, carbon nanotube (CNT),etc.

The insulating layer 112 is disposed on the first base substrate 111 tocover the pixel electrodes PEs.

The black matrix BM is disposed on the insulating layer 112. The blackmatrix BM has a lattice shape and includes openings OPs corresponding tothe pixels PXs, respectively. Hereinafter, one opening is indicated byOP and two or more openings are indicated by OPs.

The black matrix BM is extended in the driving direction of theelectrowetting layer 130. The configuration and function of the blackmatrix BM will be described in detail below with reference to FIGS. 3Aand 3B. The black matrix BM prevents light leaking through a boundaryarea between adjacent pixels PXs when the pixels PXs are driven.

The hydrophobic layer 113 has hydrophobicity and is disposed on theinsulating layer 112. The hydrophobic layer 113 is disposed in theopenings OPs of the black matrix BM.

The partition wall WA partitions the pixels PXs and is disposed on theblack matrix BM. The partition wall WA at least partially overlaps theblack matrix BM. The partition wall WA may be formed of the samematerial as the black matrix BM, so that the partition wall WA has ablack color. That is, the partition wall WA and the black matrix BM areformed of the same organic material and have a black color.

The second substrate 120 includes a second base substrate 121 facing thefirst base substrate 111 and a common electrode CE disposed on thesecond base substrate 121.

The second base substrate 121 can be formed of the same material as thefirst base substrate 111, though it can also be formed of any othersuitable material. When each of the first and second base substrates 111and 121 is a plastic substrate, the first and second base substrates 111and 121 may be flexible.

The common electrode CE is applied with a common voltage. The commonelectrode CE includes a transparent conductive material, e.g., indiumtin oxide.

Although not shown in FIG. 2, the first substrate 110 or the secondsubstrate 120 may include color filters, each of which has a color pixelthat represents one of red, green, and blue (as well as any other)colors.

The electrowetting layer 130 includes a first fluid 131 and a secondfluid 132, which are immiscible with each other. The first fluid 131 haselectrical non-conductivity or a non-polarity and the second fluid 132has electrical conductivity or a polarity. In addition, the first fluid131 has hydrophobicity and the second fluid 132 has hydrophilicity. Asexamples, the first fluid 131 may include an organic solvent, such assilicon oil, mineral oil, carbon tetrachloride (CCL₄), etc. The secondfluid 132 may include an aqueous solution and electrolyte, such assodium chloride (NaCl).

The first fluid 131 includes a black dye or a material absorbing light,to absorb the light incident thereto. In addition, the first fluid 131is dispersed over each pixel PX in a reset driving operation, or movesto a side portion of each pixel PX when it is applied with thegray-scale voltage so as to serve as a light shutter. The second fluid132 may be transparent, and thus the second fluid 132 may transmit thelight incident thereto.

As an exemplary embodiment, the first fluid 131 includes a dyerepresenting one of red, green, and blue colors or a materialrepresenting one of red, green, and blue colors. In this case, the colorfilter may be removed from the electrowetting display device 100

The movement of the electrowetting layer 130 is controlled by thegray-scale voltages respectively applied to the pixel electrodes PEs andthe common voltage applied to the common electrode CE, therebydisplaying desired images. The operation of the pixels PXs will bedescribed in detail later with reference to FIGS. 3A to 5B.

FIG. 2 shows the configuration of an electrowetting display device usedas a transmission type display device. However, the electrowettingdisplay device may be used as a reflection type display device. Althoughnot shown in the figures, in a case that the electrowetting displaydevice 100 is used as a reflection type display device, theelectrowetting display device 100 may further include a reflective layerconfigured to include a reflective metal, e.g., aluminum and/oraluminum-neodymium. The reflective layer is disposed on the pixelelectrodes PEs or under the first substrate 111.

Alternatively, the pixel electrode 112 may be configured to includereflective metal, e.g., aluminum, to reflect light instead of thereflective layer of the electrowetting display device 100.

FIG. 3A is a plan view showing a reset state of a pixel of theelectrowetting display device shown in FIG. 1, and FIG. 3B is across-sectional view taken along a line I-I′ shown in FIG. 3A.

In the present exemplary embodiment, the pixels PXs each have the sameconfiguration and function, and thus hereinafter one pixel PX will bedescribed in detail as a representative example. In FIGS. 3A and 3B, anupper direction of the pixel PX in plan view corresponds to a leftdirection of the pixel PX in the cross-sectional view, and a lowerdirection of the pixel PX in the plan view corresponds to a rightdirection of the pixel PX in the cross-sectional view.

Referring to FIGS. 3A and 3B, a side range of the pixel PX correspondsto an area between two dotted lines P and P′ shown in FIG. 3B.

The first fluid 131 and the second fluid 132 are immiscible and makecontact with each other, so a boundary exists between the first andsecond fluids 131 and 132. As shown in FIG. 3B, the first fluid 131 isaccommodated in a space defined by adjacent partition walls WA and thesecond fluid 132 is disposed on the first fluid 131.

The pixel PX partitioned by the partition walls WA includes an area inwhich the pixel electrode PE is not formed (hereinafter, referred to asa non-pixel electrode area).

When the gray-scale voltage is applied to the pixel PX, the first fluid131 of the electrowetting layer 130 is gathered in an area including thenon-pixel electrode area A of the pixel PX. When the pixel PX is reset,the first fluid 131 is dispersed over the pixel PX again. That is, dueto the non-pixel electrode area A, the electrowetting layer 130 movesbetween the upper and lower directions of the pixel PX (i.e. coveringand not covering the pixel electrode area) in the plan view while beingoperated. This operation of the pixel PX will be described in detaillater.

The black matrix BM includes a first extension portion 10 extended in adriving direction (the direction of movement of the fluid 131) of theelectrowetting layer 130 and a second extension portion 20 extended in anon-driving direction of the electrowetting layer 130. For instance,when the driving direction of the electrowetting layer 130 is the upperand lower directions of the pixel PX in plan view, the non-drivingdirection of the electrowetting layer 130 is the left and rightdirection of the pixel PX in the plan view.

The first extension portion 10 has a first width W1 and the secondextension portion 20 has a second width W2. The first width W1 isdefined by a width of two openings OPs adjacent to each other in thedriving direction of the electrowetting layer 130, and the second widthW2 is defined by a width of two openings OPs adjacent to each other inthe non-driving direction of the electrowetting layer 130.

In detail, when the driving direction of the pixel PX is the upper andlower directions in plan view, the first width W1 is defined by thewidth of two openings OPs adjacent to each other in the upper and lowerdirections, and the second width W2 is defined by the width of twoopenings OPs adjacent to each other in the left and right directions.

The first width W1 is set greater than the second width W2. The secondwidth W2 is greater than a width of the partition wall WA whichcorresponds to a width between two pixels PXs adjacent to each other.Although not shown in the figures, the second width W2 may be the sameas the width of the partition wall WA. Indeed, each width W1, W2 cantake on any suitable value.

The first extension portion 10 extends in the driving direction andincludes a first area B1, a second area B2, and a third area B3. Thefirst and second areas B1 and B2 extend in opposite directions to eachother and the third area B3 overlaps the partition wall WA.

The second area B2 extends into the area in which the first fluid 131 isgathered or in the non-pixel electrode area when the pixel PX isoperated. The first area B1 extends in the opposite direction as that ofthe second area B2.

In other words, in the case that the driving direction of theelectrowetting layer 130 is the upper and lower direction of the pixelPX in the plan view, the second area B2 is extended in the lowerdirection of the pixel PX in the plan view of FIG. 3A. The first area B1is extended in the upper direction of the pixel PX in the plan view ofFIG. 3A. The third area B3 has the same width as the partition wall WAand overlaps the partition wall WA.

A length of the pixel PX in the driving direction of the electrowettinglayer 130 is referred to as a first length L1. The first length L1includes a second length L2 and a third length L3. The second length L2indicates a length of the area of the pixel PX which does not overlapthe first area B1, and the third length L3 indicates a length of thearea of the pixel PX which does overlap the first area B1.

The width of the first area B1 may be smaller than half of the firstlength L1, and the width of the second area B2 may be smaller than thewidth of the first area B1.

When the gray-scale voltage is not applied to the pixel electrode PE,the first fluid 131 is dispersed over the pixel PX as shown in FIGS. 3Aand 3B. For example, when the pixel electrode PE and the commonelectrode CE are applied with voltages with the same voltage level, thesecond fluid 132 is not polarized since no voltage difference existsbetween the pixel electrode PE and the common electrode CE.

Upper surfaces of the first and second areas B1 and B2 of the blackmatrix BM may be surface-treated using a hydrophobic material. The firstfluid 131 having non-polarity makes contact with the hydrophobic layer113 having hydrophobicity, as well as the upper surfaces of the firstand second areas B1 and B2 of the black matrix BM. Thus, the first fluid131 may be dispersed over the pixel PX. In addition, since the firstfluid 131 absorbs light, the pixel PX displays a black gray scale.

FIG. 4A is a plan view showing a driving state of a pixel of theelectrowetting display device shown in FIG. 1, and FIG. 4B is across-sectional view taken along a line II-II′ shown in FIG. 4A.

Referring to FIGS. 4A and 4B, the pixel electrode PE is applied with thegray-scale voltage Vgray and the common electrode CE is applied with thecommon voltage Vcom. In detail, the gray-scale voltage Vgray applied tothe pixel electrode PE has a voltage level lower than that of the commonvoltage Vcom. In this, case, the common voltage Vcom is a positivevoltage and the gray-scale voltage Vgray is a negative voltage.

The second fluid 132 is polarized by the level difference between thecommon voltage Vcom and the gray-scale voltage Vgray. For instance, asshown in FIG. 4B, the pixel electrode PE has negative polarity and anarea of the second fluid 132, which is adjacent to the pixel electrodePE, has positive polarity. An attractive force acts between the pixelelectrode PE having negative polarity and the area of the second fluid,which is adjacent to the pixel electrode PE and has positive polarity.Thus, a surface tension of the polarized second fluid 132 is changed, sothat the second fluid 132 makes contact with the hydrophobic layer 113overlapped with the pixel electrode EP and the upper surface of thefirst area B1 of the black matrix BM. As a result, the first fluid 131is pushed out to a side portion of the pixel PX by the second fluid 132.

The first fluid 131 includes an organic solvent, and tends to gather.Accordingly, the first fluid 131 is pushed out to the side portion ofthe pixel PX by the second fluid 132 and stably gathered in the sideportion of the pixel PX.

For instance, since the pixel electrode PX is not formed in thenon-pixel electrode area A, the gray-scale voltage Vgray is not appliedto the non-pixel electrode area A, and therefore an electric field isnot generated in the non-pixel electrode area A. As a result, the firstfluid 131 gathers in the side portion of the pixel PX, which includesthe non-pixel electrode area A. That is, as shown in FIG. 4A, the firstfluid 131 gathers at the upper portion of the pixel PX. In addition, asshown in FIG. 4B, the first fluid 131 may be gathered to the leftportion of the pixel PX. In this case, the light transmits through thesecond fluid 132, so that the pixel PX displays a predetermined image.

As described above, the second area B2 of the black matrix BM extendsinto the area in which the first fluid 131 is gathered. Accordingly, thesecond area B2 overlaps with the area in which the first fluid 131 isgathered.

In detail, as shown in FIG. 4B, the second area B2 of the black matrixBM overlaps with a predetermined area in which the first fluid 131gathers. Although not shown in the figures, in the case that the widthof the second area B2 is smaller than the width of the first area B1,the second area B2 may overlap the entire area in which the fluid 131 isgathered.

Ideally, the first fluid 131 has a light blocking rate of 100%, but thelight blocking rate of the first fluid 131 may not be 100%. Accordingly,a portion of the light incident to the first substrate 110 may transmitthrough the first fluid 131 gathered in the non-pixel electrode area A.Since the second area B2 of the black matrix BM overlaps with the areain which the first fluid 131 is gathered, the second area B2 of theblack matrix BM may serve as a shutter to at least partially block thelight passing through the first fluid 131.

The amount of the first fluid 131 pushed into non-pixel electrode area Adepends on the level difference between the gray-scale voltage Vgrayapplied to the pixel electrode PE and the common voltage Vcom applied tothe common electrode CE. For example, as the level difference betweenthe common voltage CE and the gray-scale voltage Vgray increases, theamount of the first fluid 131 gathered in the non-pixel electrode area Aincreases. The common voltage CE has a constant level and the gray-scalevoltage Vgray has a level corresponding to the gray-scale displayed inthe pixel PX. Thus, the pushed-out amount of the first fluid 131 may bedecided by the level of the gray-scale voltage Vgray applied to thepixel electrode 112.

The first fluid 131 pushed out to the side portion of the pixel PX has aheight greater than a height of the partition wall WA as shown in FIG.4B. A side surface of the partition wall WA is surface-treated to havehydrophilicity, and an upper surface of the partition wall WA issurface-treated to have hydrophobicity. Thus, the first fluid 131 has achemical affinity to the side surface of the partition wall WA, which ishigher than a chemical affinity to the upper surface of the partitionwall WA. As a result, although the first fluid 131 has the height higherthan that of the partition wall WA, the first fluid 131 may be preventedfrom moving to adjacent pixel beyond the partition wall WA.

FIG. 5A is a plan view showing a movement of an electrowetting layer ofa pixel in a reset state, and FIG. 5B is a cross-sectional view takenalong a line III-III′ shown in FIG. 5A.

Referring to FIGS. 5A and 5B, the first fluid 131 gathered in thenon-pixel electrode area A is dispersed over the pixel PX when the pixelPX is reset. For instance, the first fluid 131 gathered in the non-pixelelectrode area A moves to the lower direction of the pixel PX in theplan view shown in FIG. 5A when the pixel PX is reset. In addition, thefirst fluid 131 gathered in the non-pixel electrode area A moves to theright direction of the pixel PX in the cross-sectional view shown inFIG. 5B when the pixel PX is reset.

When the pixel PX is reset, the moving speed of the first fluid 131 maynot be uniform in the pixel PX. In detail, the second length L2 has alength corresponding to approximately seven-tenths of the first lengthL1, and the third length L3 has a length corresponding to approximatelythree-tenths of the first length L1. When an average speed of the firstfluid 131 moving through the plan area of the pixel PX corresponding tothe second length L2 is referred to as a first speed, and an averagespeed of the first fluid 131 moving through the plan area of the pixelPX corresponding to the third length L3 is referred to as a secondspeed, the first speed may be faster than the second speed. Theoperation time of the pixel PX corresponds to a sum of a time requiredto display a predetermined gray scale and a time required to display theblack gray-scale.

In a case that the first fluid 131 moves to the boundary surface of thefirst area B1 of the black matrix BM, the light incident to the area ofthe pixel PX, which corresponds to the first area B1, is blocked by theblack matrix BM. In detail, the black matrix BM extends through thethird length L3 and the first fluid 131 moves through the plan area ofthe pixel PX corresponding to the second length L2 at the first speed.In this case, the light provided to the plan areas of the pixel PX,which corresponds to the third length L3, is blocked by the first areaB1 of the black matrix BM. Accordingly, the pixel PX may display theblack gray-scale before the first fluid 131 is dispersed over the pixelPX.

The first fluid 131 may move through the plan area of the pixel PX,which corresponds to the third length L3, at the second speed slowerthan the first speed. The light is blocked by the first area B1 of theblack matrix BM while the first fluid 131 moves at the second speed.Accordingly, the operation time of the pixel PX may be reduced to onlythe time during which the first fluid 131 moves along the second lengthL2 at the first speed, rather than the time during which the first fluid131 moves across the entire surface of the pixel PX. When the operationtime of the pixel PX is reduced, the driving speed of the pixel PX maybe improved.

Consequently, the electrowetting display device 100 according to thefirst exemplary embodiment may improve the driving speed of the pixelPX.

As described above, the first extension portion 10 of the black matrixBM includes the first area B1 extended in the upper direction of thepixel PX in the plan view, and the second area B2 extended in the lowerdirection of the pixel PX in the plan view, but the black matrix BMshould not be limited thereto or thereby. For instance, in the case thatthe driving direction of the electrowetting layer 130 is the left andright directions of the pixel PX in the plan view, the second extensionportion 20 of the black matrix BM includes first and second areas B1 andB2 respectively extended in the left and right directions of the pixelPX in the plan view.

In addition, the driving direction of the electrowetting layer 130 maybe a diagonal direction. For example, the non-pixel electrode area A maybe disposed at one corner of a rectangular pixel PX. Therefore, thefirst fluid 131 gathers in the corner at which the non-pixel electrodearea A is formed. In this case, the black matrix BM includes a secondarea B2 partially overlapping the area in which the first fluid 131 isgathered, and a first area B1 extended opposite to the second area B2along the diagonal direction.

FIG. 6 is a cross-sectional view showing an electrowetting displaydevice according to a second exemplary embodiment of the presentinvention.

The electrowetting display device 200 according to the second exemplaryembodiment has the same structure and function as those of theelectrowetting display device 100 shown in FIG. 1 according to the firstexemplary embodiment, except for the first substrate 110. In FIG. 6, thesame reference numerals denote the same elements in FIGS. 1 to 5A and5B, and thus detailed descriptions of the same elements will be omitted.

Referring to FIG. 6, a black matrix BM and a pixel electrode PE aredisposed on a first base substrate 111 of the first substrate 110.

The black matrix BM has substantially the same configuration as theblack matrix shown in FIG. 3A. For instance, the black matrix BMincludes a first extension portion 10 and a second extension portion(not shown). The first extension portion 10 includes a first area B1, asecond area B2, and a third area B3.

A portion of the black matrix BM overlaps, and makes contact with, aportion of the pixel electrode PE. The portion of the black matrix Bwhich overlaps the portion of the pixel electrode PE includes a portionof the first area B1 and the third area B3 as shown in FIG. 6. The uppersurface of the black matrix BM makes contact with the lower surface ofthe pixel electrode PE in the area of overlap, but embodiments of theinvention are not limited thereto or thereby. That is, for example, theupper surface of the pixel electrode PE may make contact with the lowersurface of the black matrix BM in the overlapped area.

An insulating layer 112 is disposed on the first base substrate 111 tocover the black matrix BM and the pixel electrode PE. A hydrophobiclayer 113 is disposed on the insulating layer 112.

A partition wall WA is disposed on the hydrophobic layer 113 topartition pixels PXs. The partition wall WA is formed of photoresist orby patterning an insulating layer, e.g., silicon nitride (SiNx), siliconoxide (SiOx), etc. Different from the electrowetting display device 100according to the first exemplary embodiment, the partition wall WA ofthe electrowetting display device 200 according to the second exemplaryembodiment does not have a black color.

Hereinafter, the second substrate 120 and the electrowetting layer 130have the same structure and function as those of the electrowettingdisplay device 100 according to the first exemplary embodiment, and thusdetailed descriptions of the second substrate 120 and the electrowettinglayer 130 will be omitted.

When the pixel electrode PE is applied with a gray-scale voltage and thecommon electrode CE is applied with a common voltage, the second fluid132 of the electrowetting layer 130 is polarized. The polarized secondfluid 132 makes contact with the hydrophobic layer 113 to push out thefirst fluid 131 to a side portion of the pixel PX. Accordingly, thefirst fluid 131 may be gathered in an area of the pixel PX whichincludes the non-pixel electrode area A.

When the pixel PX is reset, the first fluid 131 makes contact with thehydrophobic layer 113 so as to be dispersed over the pixel PX. Since theoperation of the pixel PX has been described already, details thereofwill be omitted.

When the pixel PX is reset, the first fluid 131 moves to the boundarysurface of the first area B1 of the black matrix BM. In this case, thelight incident to the area of the pixel PX, which corresponds to thefirst area B1, is blocked by first area B1 of the black matrix BM.

When the gray-scale voltage is applied to the pixel PX, the second areaB2 of the black matrix BM blocks the light passing through the firstfluid 131 gathered in the side portion of the pixel PX.

Consequently, the electrowetting display device 100 according to thesecond exemplary embodiment may improve the driving speed of the pixelPX.

FIG. 7 is a cross-sectional view showing an electrowetting displaydevice according to a third exemplary embodiment of the presentinvention.

The electrowetting display device 300 according to the third exemplaryembodiment has the same structure and function as those of theelectrowetting display device 200 shown in FIG. 6 according to thesecond exemplary embodiment, except for the partition wall WA. In FIG.7, the same reference numerals denote the same elements in FIG. 6, andthus detailed descriptions of the same elements will be omitted.

Referring to FIG. 7, the partition wall WA that partitions the pixelsPXs is disposed on the hydrophobic layer 113. The partition wall WA isformed of the same material as the black matrix BM, and has a blackcolor. In detail, the partition wall WA and the black matrix BM areformed of an organic material and have a black color.

The black matrix BM has a substantially similar configuration as theblack matrix BM shown in FIG. 6, and the other elements of theelectrowetting display device 300 according to the third exemplaryembodiment have substantially the same configuration as theelectrowetting display device 200 according to the second exemplaryembodiment, and thus details thereof will be omitted.

Due to the configuration of the black matrix BM, the electrowettingdisplay device 300 according to the third exemplary embodiment mayimprove the driving speed of the pixel PX.

FIG. 8 is a cross-sectional view showing an electrowetting displaydevice according to a fourth exemplary embodiment of the presentinvention.

The electrowetting display device 400 according to the fourth exemplaryembodiment has the same structure and function as those of theelectrowetting display device 200 shown in FIG. 6 according to thesecond exemplary embodiment, except that the black matrix BM is formedon the second substrate rather than the first substrate. In FIG. 8, thesame reference numerals denote the same elements in FIG. 6, and thusdetailed descriptions of the same elements will be omitted.

Referring to FIG. 8, the second substrate 120 includes a second basesubstrate 121, a black matrix BM and a planarization layer 122 eachdisposed on the second base substrate 121, and a common electrode CEdisposed on the black matrix BM and the planarization layer 122.

The black matrix BM includes a plurality of openings formedtherethrough, and the planarization layer 122 is disposed in theopenings. FIG. 8 shows one opening OP formed through the black matrixBM, with the planarization layer 122 being disposed in the opening OP.

The planarization layer 122 has a height equal to a height of the blackmatrix BM. Accordingly, the common electrode CE may have a flat surfaceas shown in FIG. 8.

The black matrix BM has a substantially similar configuration as that ofthe black matrix BM shown in FIG. 6. That is, the black matrix BMincludes the first extension portion 10 and the second extension portion(not shown). The first extension portion 10 includes the first area B1,the second area B2, and the third area B3.

The first substrate 110 of the electrowettting display device 400 hassubstantially the same configuration as the first substrate 110 shown inFIG. 6, except that the first substrate 110 does not include the blackmatrix BM. In addition, the electrowetting layer 130 of theelectrowetting display device 400 has a substantially similarconfiguration as that of the electrowetting layer 130 shown in FIG. 6.Thus, detailed descriptions of the first substrate 110 and theelectrowetting layer 130 will be omitted.

When the pixel electrode PE is applied with a gray-scale voltage and thecommon electrode CE is applied with a common voltage, the second fluid132 of the electrowetting layer 130 is polarized. The polarized secondfluid 132 makes contact with the hydrophobic layer 113 to push out thefirst fluid 131 to a side portion of the pixel PX. Accordingly, thefirst fluid 131 gathers in an area of the pixel PX which includes thenon-pixel electrode area A. When the pixel PX is reset, the first fluid131 makes contact with the hydrophobic layer 113 so as to be dispersedover the pixel PX. Since the operation of the pixel PX has beendescribed already, details thereof will be omitted.

When the pixel PX is reset, the first fluid 131 moves to the boundarysurface of the first area B1 of the black matrix BM. In this case, thelight incident to the area of the pixel PX, which corresponds to thefirst area B1, is blocked by first area B1 of the black matrix BM.

When the gray-scale voltage is applied to the pixel PX, the second areaB2 of the black matrix BM blocks the light passing through the firstfluid 131 gathered in the side portion of the pixel PX.

Consequently, the electrowetting display device 100 according to thefourth exemplary embodiment may improve the driving speed of the pixelPX.

Although the exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thespirit and scope of the present invention as hereinafter claimed.

What is claimed is:
 1. An electrowetting display device comprising: a first base substrate that includes a plurality of pixels; a second base substrate that faces the first base substrate and includes a common electrode; an electrowetting layer disposed between the first base substrate and the second base substrate; a plurality of pixel electrodes disposed on the first base substrate to respectively correspond to the pixels; a black matrix that includes a plurality of openings corresponding to respective ones of the pixels, the black matrix having a first extension portion extending in a driving direction of the electrowetting layer, the driving direction being a direction in which motion of the electrowetting layer is induced when a voltage difference is applied between the common electrode and the corresponding pixel electrode, and extending in a second direction substantially perpendicular to the driving direction; and a partition wall that partitions the pixels, wherein the first extension portion comprises a first area, a second area, and a third area, the first area and the second area respectively extending in opposite directions to each other, and wherein the third area has a width substantially the same as a width of the partition wall, the first area has a width less than about half of a first length corresponding to a length extending between both sides of each pixel in the driving direction of the electrowetting layer, and the second area has a width less than the width of the first area.
 2. The electrowetting display device of claim 1, wherein the black matrix further comprises a second extension portion extending between adjacent ones of the first extension portions, and wherein the first extension portion has a width greater than a width of the second extension portion.
 3. The electrowetting display device of claim 2, wherein a width of the second extension portion is equal to or greater than a width of the partition wall.
 4. The electrowetting display device of claim 1, wherein the third area overlaps the partition wall.
 5. The electrowetting display device of claim 1, wherein the partition wall is disposed on the black matrix.
 6. The electrowetting display device of claim 5, wherein the partition wall comprises a same material as the black matrix and has a black color.
 7. The electrowetting display device of claim 1, further comprising: an insulating layer disposed on the first base substrate to cover the pixel electrodes; and a hydrophobic layer disposed in the openings, wherein the black matrix and the hydrophobic layer are both disposed on the insulating layer.
 8. The electrowetting display device of claim 7, wherein the electrowetting layer comprises: a first fluid that has electrical non-conductivity or non-polarity; and a second fluid immiscible with the first fluid and having an electrical conductivity or a polarity, wherein the first fluid is accommodated in a space defined by the partition wall, and the second fluid is disposed on the first fluid.
 9. The electrowetting display device of claim 8, wherein when a common voltage is applied to the common electrode and one or more gray-scale voltages are applied to the pixel electrodes, the second fluid contacts the hydrophobic layer and the first areas so as to push the first fluid to a side portion of the pixels.
 10. The electrowetting display device of claim 9, wherein the second area extends under an area in which the first fluid is gathered, so as to overlap the first fluid.
 11. The electrowetting display device of claim 1, wherein the width of the first area is equal to or greater than about three-tenths of the first length.
 12. The electrowetting display device of claim 1, further comprising: an insulating layer disposed on the first base substrate to cover the black matrix and the pixel electrodes; and a hydrophobic layer disposed on the insulating layer, wherein the black matrix is disposed on the first base substrate, the partition wall is disposed on the hydrophobic layer, and the first area overlaps a predetermined area of the pixel electrode to make contact with the pixel electrode.
 13. The electrowetting display device of claim 12, wherein the partition wall has a black color.
 14. An electrowetting display device comprising: a first base substrate that includes a plurality of pixels; a second base substrate that faces the first base substrate and includes a common electrode; an electrowetting layer disposed between the first base substrate and the second base substrate; a plurality of pixel electrodes disposed on the first base substrate to respectively correspond to the pixels; a black matrix disposed between the common electrode and the second base substrate and including a plurality of openings corresponding to respective ones of the pixels, the black matrix having a first extension portion extending in a driving direction of the electrowetting layer, the driving direction being a direction in which motion of the electrowetting layer is induced when a voltage difference is applied between the common electrode and the corresponding pixel electrode, and extending in a second direction substantially perpendicular to the driving direction; and a partition wall that partitions the pixels, wherein the first extension portion comprises a first area, a second area, and a third area, the first area and the second area respectively extending in opposite directions to each other, and wherein the third area has a width substantially the same as a width of the partition wall, the first area has a width less than about half of a first length corresponding to a length extending between both sides of each pixel in the driving direction of the electrowetting layer, and the second area has a width less than the width of the first area.
 15. The electrowetting display device of claim 14, wherein the black matrix further comprises a second extension portion extending between adjacent ones of the first extension portions, and wherein the first extension portion has a width greater than a width of the second extension portion and the third area of the first extension portion is overlapped with the partition wall.
 16. The electrowetting display device of claim 14, further comprising: an insulating layer disposed on the first base substrate to cover the pixel electrodes; and a hydrophobic layer disposed on the insulating layer, wherein the partition wall is disposed on the hydrophobic layer.
 17. The electrowetting display device of claim 16, wherein the electrowetting layer comprises: a first fluid that has electrical non-conductivity or non-polarity; and a second fluid immiscible with the first fluid and having an electrical conductivity or a polarity, wherein the first fluid is accommodated in a space defined by the partition wall, and the second fluid is disposed on the first fluid.
 18. The electrowetting display device of claim 17, wherein when a common voltage is applied to the common electrode and one or more gray-scale voltages are applied to the pixel electrodes, the second fluid contacts the hydrophobic layer so as to push the first fluid to a side portion of the pixels.
 19. The electrowetting display device of claim 18, wherein the second area extends under an area in which the first fluid is gathered, so as to overlap the first fluid.
 20. The electrowetting display device of claim 14, wherein the width of the first area is equal to or greater than about three-tenths of the first length. 